Control Methods for High-Speed Supercavitating Vehicles

Supercavitation is an emerging technology that enables underwater vehicles to reach un- precedented speed. With proper design of cavitator attached to the vehicle nose, the vehicle body is surrounded by water vapor cavity, eliminating skin friction drag. This technology offers unprecedented drag reduction, though poses problems for vehicle design. The gas bubble surrounding the hull introduces highly coupled dynamic behavior, representing a challenge for the control designer. Development of stable, controllable supercavitating vehi- cles requires solution for several open problems. This dissertation addresses the problem of control oriented modeling, stability augmentation, and reference tracking using parameter dependent control techniques for supercavitating vehicles.\ud The thesis is divided into three parts. A nonlinear dynamical model capturing the most important properties of the vehicle motion is developed from a control design perspective. The model includes memory effects associated with the time evolution of the cavity and uses lookup tables to determine forces.\ud To aid understanding the cavity-vehicle interaction, a longitudinal control scenario is developed for a simplified longitudinal dynamical model with guaranteed properties. Sig- nificant insight is gained on planing behavior and operating envelope using constrained control inputs.\ud Extending the longitudinal control problem, a linear parameter varying model of the coupled motion is developed to provide a platform for parameter dependent control syn- thesis. The mathematical model is scheduled with aerodynamic angles, uses steady-state approximation of the cavity, leading to uncertainty in the governing equations. Two Linear Parameter Varying (LPV) controllers are synthesized for the angle rate tracking problem, taking uncertainty into account. One uses traditional decoupled loops for pitch-, roll- and yaw-rate tracking. Ignoring the cross coupling, leads to more tractable subproblems . A controller, taking advantage of the coupling, is also presented in the thesis. The complexity of the coupled dynamics prohibits the synthesis of the controller as a single entity. Sev- eral LPV controllers synthesized for smaller overlapping regions of the parameter space are blended together, providing a single controller for the full flight envelope. Time-domain simulations of different vehicle-controller configurations, implemented on high-fidelity sim- ulations, provide insight into the capabilities of the supercavitating vehicle

Some data processing requirements for precision Nap-Of-the-Earth (NOE) guidance and control of rotorcraft

Nap-Of-the-Earth (NOE) flight in a conventional helicopter is extremely taxing for two pilots under visual conditions. Developing a single pilot all-weather NOE capability will require a fully automatic NOE navigation and flight control capability for which innovative guidance and control concepts were examined. Constrained time-optimality provides a validated criterion for automatically controlled NOE maneuvers if the pilot is to have confidence in the automated maneuvering technique. A second focus was to organize the storage and real-time updating of NOE terrain profiles and obstacles in course-oriented coordinates indexed to the mission flight plan. A method is presented for using pre-flight geodetic parameter identification to establish guidance commands for planned flight profiles and alternates. A method is then suggested for interpolating this guidance command information with the aid of forward and side looking sensors within the resolution of the stored data base, enriching the data content with real-time display, guidance, and control purposes. A third focus defined a class of automatic anticipative guidance algorithms and necessary data preview requirements to follow the vertical, lateral, and longitudinal guidance commands dictated by the updated flight profiles and to address the effects of processing delays in digital guidance and control system candidates. The results of this three-fold research effort offer promising alternatives designed to gain pilot acceptance for automatic guidance and control of rotorcraft in NOE operations

Perancangan Kendali Optimal LQT untuk Pengendalian dan Pemanduan pada Rudal

Peluru kendali (rudal) perlu dikendalikan dan dibuat untuk selalu mengikuti komando yang diberikan pemandu agar rudal dapat bergerak menuju sasarannya. Pengedalian rudal menjadi lebih rumit dikarenakan rudal memiliki persamaan dinamika yang non-linear dan coupled. Linear Quadratic Tracking (LQT) merupakan salah satu metode kendali optimal dengan tujuan membuat keluaran sistem mengikuti referensi yang diberikan sedekat mungkin dengan memperhatikan suatu indeks performansi. Sistem yang ingin dikendalikan oleh LQT harus sistem yang linier, namun rudal memiliki karakteristik yang non-linear, sehingga diperlukan linearisasi agar rudal dapat dikendalikan dengan LQT. Dalam tugas akhir ini, dirancang sebuah autopilot rudal yang terdiri dari non-linear state feedback decoupler dan pengendali LQT. Pemandu yang digunakan adalah Pemandu Pengejar (Pursuit Guidance). Simulasi pengejaran rudal menuju sasaran dirancang dengan menggunakan dua jenis sasaran, yaitu sasaran statis dan sasaran dinamis. Hasil simulasi menunjukkan dengan sasaran statis, rata-rata jarak terdekat antara rudal – sasaran sebesar 0.45 meter. Sedangkan pada sasaran dinamis, rata-rata jarak terdekat antara rudal – sasaran sebesar 2.562 meter. ============================================================================================================== Missile needs to be controlled and made to always follow the commanded guidance in order to make it engage the target. Controlling the missile has become more complex because missile has a non-linear and coupled dynamic equation. Linear Quadratic Tracking (LQT) is one method of optimal control theory where its objective is to make the output of a system tracks its reference as close as possible while minimize or maximize a performance index. The system which wants to be controlled with LQT must be a linear system, but the missile itself has a non-linear system, so the missile needs to be linearized in order to control it using LQT. In this final project, a missile’s autopilot is designed which consists of non-linear state feedback decoupler and LQT controller. Pursuit Guidance is used for the guidance law. A missile – target engagement simulation is made and done using 2 kinds of targets; static target and dynamic target. From the simulation result’s by using static target, the mean of the closest distance between the missile and the target is 0.45 meters and from the simulation result’s by using dynamic target, the mean of the closest distance between the missile and the target is 2.562 meters

Control Design and Performance Analysis for Autonomous Formation Flight Experimentss

Autonomous Formation Flight is a key approach for reducing greenhouse gas emissions and managing traffic in future high density airspace. Unmanned Aerial Vehicles (UAV\u27s) have made it possible for the physical demonstration and validation of autonomous formation flight concepts inexpensively and eliminates the flight risk to human pilots. This thesis discusses the design, implementation, and flight testing of three different formation flight control methods, Proportional Integral and Derivative (PID); Fuzzy Logic (FL); and NonLinear Dynamic Inversion (NLDI), and their respective performance behavior. Experimental results show achievable autonomous formation flight and performance quality with a pair of low-cost unmanned research fixed wing aircraft and also with a solo vertical takeoff and landing (VTOL) quadrotor

Control Design and Performance Analysis for Autonomous Formation Flight Experiments

Autonomous Formation Flight is a key approach for reducing greenhouse gas emissions and managing traffic in future high density airspace. Unmanned Aerial Vehicles (UAV’s) have made it possible for the physical demonstration and validation of autonomous formation flight concepts inexpensively and eliminates the flight risk to human pilots. This thesis discusses the design, implementation, and flight testing of three different formation flight control methods, Proportional Integral and Derivative (PID); Fuzzy Logic (FL); and NonLinear Dynamic Inversion (NLDI), and their respective performance behavior. Experimental results show achievable autonomous formation flight and performance quality with a pair of low-cost unmanned research fixed wing aircraft and also with a solo vertical takeoff and landing (VTOL) quadrotor

Nonlinear Tracking Control Using a Robust Differential-Algebraic Approach.

This dissertation presents the development and application of an inherently robust nonlinear trajectory tracking control design methodology which is based on linearization along a nominal trajectory. The problem of trajectory tracking is reduced to two separate control problems. The first is to compute the nominal control signal that is needed to place a nonlinear system on a desired trajectory. The second problem is one of stabilizing the nominal trajectory. The primary development of this work is the development of practical methods for designing error regulators for Linear Time Varying systems, which allows for the application of trajectory linearization to time varying trajectories for nonlinear systems. This development is based on a new Differential Algebraic Spectral Theory. The problem of robust tracking for nonlinear systems with parametric uncertainty is studied in relation to the Linear Time Varying spectrum. The control method presented herein constitutes a rather general control strategy for nonlinear dynamic systems. Design and simulation case studies for some challenging nonlinear tracking problems are considered. These control problems include: two academic problems, a pitch autopilot design for a skid-to-turn missile, a two link robot controller, a four degree of freedom roll-yaw autopilot, and a complete six degree of freedom Bank-to-turn planar missile autopilot. The simulation results for these designs show significant improvements in performance and robustness compared to other current control strategies

Formalizing the Future: How Central Banks Set Out to Govern Expectations but Ended Up (En-)Trapped in Indicators

Modern ‘inflation targeting’ monetary policy has been one of the prototypes of future-oriented modes of social coordination which in recent years have captured the sociological imagination. Modern central banking is commonly presented as achieving greater efficacy by directly managing economic expectations, in particular when contrasted with the previous heavy-handed, “hydraulic” transmission of policy objectives through systems of economic aggregates. Such empirical claims are mirrored in the theoretical distinction drawn by sociologists between the openness and efficacy of future-oriented coordination of expectations, and the more rigid coordination achieved through formal organizing and formalization. This paper uses the case of the US Federal Reserve’s (Fed) transition to inflation targeting in the 1980s to show how the precision and flexibility of social coordination through expectations in fact relies on extensive formalization and rigid proceduralization. I show that the tightly coupled control relation on which inflation targeting rests is not possible without the constitutive exclusion of other modes of representing and intervening the economy achieved by this formalization. However, the price for the robust and precise reactivity that modern central banking has constructed between key indicators of inflation expectations and the interest rate set by monetary policy is a comprehensive procedural dis-embedding of monetary policy from the structure of economic activities whose path into the future it is meant to govern. The paper concludes that in order to better understand the conditions under which future-oriented modes of coordination fail or succeed, we need to study more closely the formalization of social relations on which they are founded

Aeronautical engineering: A continuing bibliography with indexes (supplement 319)

This report lists 349 reports, articles and other documents recently announced in the NASA STI Database. The coverage includes documents on the engineering and theoretical aspects of design, construction, evaluation, testing, operation, and performance of aircraft (including aircraft engines) and associated components, equipment, and systems. It also includes research and development in aerodynamics, aeronautics, and ground support equipment for aeronautical vehicles

Motion primitives and 3D path planning for fast flight through a forest

This paper presents two families of motion primitives for enabling fast, agile flight through a dense obstacle field. The first family of primitives consists of a time-delay dependent 3D circular path between two points in space and the control inputs required to fly the path. In particular, the control inputs are calculated using algebraic equations which depend on the flight parameters and the location of the waypoint. Moreover, the transition between successive maneuver states, where each state is defined by a unique combination of constant control inputs, is modeled rigorously as an instantaneous switch between the two maneuver states following a time delay which is directly related to the agility of the robotic aircraft. The second family consists of aggressive turn-around (ATA) maneuvers which the robot uses to retreat from impenetrable pockets of obstacles. The ATA maneuver consists of an orchestrated sequence of three sets of constant control inputs. The duration of the first segment is used to optimize the ATA for the spatial constraints imposed by the turning volume. The motion primitives are validated experimentally and implemented in a simulated receding horizon control (RHC)-based motion planner. The paper concludes with inverse-design pointers derived from the primitives

Investigation of external refrigeration systems for long term cryogenic storage

Selection and optimization of space cryogenic storage tank